LINQ、INNER (Join或GroupJoin)？

// 定义一个学生类
public class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public int DepartmentId { get; set; }
}

// 定义一个部门类
public class Department
{
    public int Id { get; set; }
    public string Name { get; set; }
}

// 示例数据
List<Student> students = new List<Student>
{
    new Student { Id = 1, Name = "Alice", Age = 20, DepartmentId = 1 },
    new Student { Id = 2, Name = "Bob", Age = 22, DepartmentId = 2 },
    new Student { Id = 3, Name = "Charlie", Age = 21, DepartmentId = 1 }
};

List<Department> departments = new List<Department>
{
    new Department { Id = 1, Name = "IT Department" },
    new Department { Id = 2, Name = "Marketing Department" }
};

// INNER JOIN示例：查询学生及其所属部门的名称
var innerJoinQuery = from student in students
                     join department in departments on student.DepartmentId equals department.Id
                     select new { student.Name, department.Name };

foreach (var result in innerJoinQuery)
{
    Console.WriteLine($"Student: {result.Name}, Department: {result.Name}");
}

// GROUP JOIN示例：查询部门及其所属学生的名称列表
var groupJoinQuery = from department in departments
                     join student in students on department.Id equals student.DepartmentId into studentGroup
                     select new { DepartmentName = department.Name, Students = studentGroup };

foreach (var result in groupJoinQuery)
{
    Console.WriteLine($"Department: {result.DepartmentName}");
    foreach (var student in result.Students)
    {
        Console.WriteLine($"- Student: {student.Name}");
    }
    Console.WriteLine();
}